Heretofore, hard gelatin capsules were used principally or only to contain powdery or grainy pharmaceutical products. The capsule-filling machinery for the powder substances generally prepares a powder plug which is inserted into one-half of the gelatin capsule. However, the demands of the pharmaceutical industry include the desirability of placing liquids into hard gelatine capsules. This process involves certain difficulties among which are, firstly, that the two-piece capsule is not necessarily fluid-tight and, secondly, that if the lower capsule half is filled with liquid, that liquid will spill over during a further transporting of the capsule from the filling station to the closure station. Such spillage might be avoided by filling the capsule only partially. However, a partial filling might have negative consumer response due to the suspicion of having produced a so-called "cheated package". Furthermore, the filling efficiency of such a capsule is reduced, resulting in additional packaging costs. Again, a substantially reduced filling factor would make it impossible to package the dosages required in customary capsule sizes.
In order to overcome the aforementioned difficulties, the pharmaceutical industry has developed a fluid containing the medicinal product which congeals after being placed into one-half of a gelatin capsule. The fact that the fluid is capable of congealing makes certain demands on the filling pump, for example the medium must remain fluid during the filling process within the pump and the pump nozzle and must not be permitted to congeal therein.